Tweening the transparency of a model?

Hi, im trying to tween the transparency of a model. This is the script im trying out

local ts = game:GetService("TweenService")
local info = TweenInfo.new(4)

local function tweenModel(model)
    local tr = Instance.new("IntValue")
    tr.Value = 0
    local parts = model:GetChildren()

    tr:GetPropertyChangedSignal("Value"):Connect(function()
        for i,v in pairs(parts) do
            if v.ClassName == "Part" or v.ClassName == "UnionOperation" then
                v.Transparency = tr.Value
            end
        end
    end)

    local tween = ts:Create(tr, info, {Value = 1})
    tween:Play()

    tween.Completed:connect(function()
        tr:Destroy()
        model:Destroy()
    end)
end

But the model just dissapears in under a second. Is there a way to make it disappear slow? I think it doesnt even set the transparency up but just destroy the model in the end.