Trying to add global security groups to a folder - powershell

Question

I wrote a script to create a new folder based on some company variables and later on add a group with users to handle the permissions on this folder.
I can not find a decent way to add one, or more, AD groups to a folder in the same script.
Here is my script:
$parentfolder = Read-Host -Prompt "Please enter the name of the parent folder (i.e. FOLDER1234)"
$folder = Read-Host -Prompt "Please enter the name of the new network folder"
New-Item \\DC02\product\$parentfolder\$folder -type directory
Write-Host "Folder has been created!"
Start-Sleep -s 2
$newgroup = Read-Host -Prompt "Please enter the new group name for this folder (1234-1234-12xx format)"
$description = Read-Host -Prompt "Please enter the abbreviation of the product (i.e. PDPROD)"
NEW-ADGroup -Name $newgroup -GroupScope Global -Description $description -Path "OU=Project Groups,DC=ourdomain,DC=nl"
do {
$stringquit = Read-Host -Prompt "Please enter the member username's to add or press Q if you are done."
$userfilter3 = Get-ADUser -Filter {sAMAccountName -eq $stringquit}
if ($userfilter3 -eq $Null,"Q") {
Write-Host = "User does not exist in AD, please try again"
Start-Sleep -s 1
} else {
if ($stringquit -ne "Q") {
Write-Output -InputObject $stringquit | Out-File -Append c:\userlist.csv
} else {
Write-Host "You pressed Q, moving on."
}
}
} until ($stringquit -eq "Q")
$addgroup = "cn=$newgroup,ou=Project Groups,dc=ourdomain,dc=nl"
$list = Get-Content c:\userlist.csv
foreach ($user in $list) {
Add-ADGroupMember -Identity $addgroup -Member $user
}
#set permissions
$acl = Get-Acl \\DC02\product\$parentfolder\$folder
$ar = New-Object System.Security.AccessControl.FileSystemAccessRule("1234-all","Modify"."ContainerInherit,ObjectInherit","None","Allow")
$acl.SetAccessRule($ar)
Set-Acl \\DC02\product\$parentfolder\$folder $acl

Answer 1

Replace SetAccessRule() with AddAccessRule().